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1. Interpreting and reporting 40Ar/39Ar geochronologic data

   https://doi.org/10.1130/B35560.1  

   Schaen, Allen J.; Jicha, Brian R.; Hodges, Kip V.; Vermeesch, Pieter; Stelten, Mark E.; Mercer, Cameron M.; Phillips, David; Rivera, Tiffany A.; Jourdan, Fred; Matchan, Erin L.; et al (July 2020, GSA Bulletin)

   null (Ed.)

   Abstract The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide range of geologic and extraterrestrial processes. Analyses of increasingly smaller subsamples have revealed age dispersion in many materials, including some minerals used as neutron fluence monitors. Accordingly, interpretive strategies are evolving to address observed dispersion in dates from a single sample. Moreover, inferring a geologically meaningful “age” from a measured “date” or set of dates is dependent on the geological problem being addressed and the salient assumptions associated with each set of data. We highlight requirements for collateral information that will better constrain the interpretation of 40Ar/39Ar data sets, including those associated with single-crystal fusion analyses, incremental heating experiments, and in situ analyses of microsampled domains. To ensure the utility and viability of published results, we emphasize previous recommendations for reporting 40Ar/39Ar data and the related essential metadata, with the amendment that data conform to evolving standards of being findable, accessible, interoperable, and reusable (FAIR) by both humans and computers. Our examples provide guidance for the presentation and interpretation of 40Ar/39Ar dates to maximize their interdisciplinary usage, reproducibility, and longevity. 

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2. Precambrian to Pleistocene 40Ar/39Ar dating of clinopyroxene-hosted melt inclusions

   https://doi.org/10.1130/G51777.1  

   Jicha, Brian R; Schaen, Allen J; Wathen, Bryan; Nachlas, William O (February 2024, Geology)

   Abstract Clinopyroxene is a rock-forming mineral that commonly hosts melt inclusions in mafic to intermediate composition volcanic and plutonic rocks. It is highly resistant to alteration compared to other co-existing phenocrysts such as plagioclase. Several recent studies have 40Ar/39Ar dated clinopyroxene in Neoproterozoic to Miocene basalts and dolerites. To assess the viability of the technique at the youngest end of the geologic time scale, we performed 40Ar/39Ar incremental heating experiments on clinopyroxene-hosted melt inclusions from a variety of mafic lithologies and tectonic settings. Most samples produced precise plateau ages including several Quaternary basalts to andesites as young as 0.6 Ma. All data are indistinguishable from new and/or published 40Ar/39Ar ages on groundmass or plagioclase from the same samples. The source of potassium (K) and resulting 40Ar* within clinopyroxene has been debated, but thus far has only been inferred based on 40Ar/39Ar data. Using electron probe microanalysis (EPMA) we show that there is negligible K in the clinopyroxene host, but substantial K (e.g., 1–4 wt%) in trapped melt inclusions and minor amounts in plagioclase inclusions. Thus, melt inclusions, which are common in phenocrysts in basaltic magmas, can be used to obtain accurate and precise 40Ar/39Ar ages for difficult-to-date volcanic and plutonic rocks from the Precambrian to the Pleistocene. 

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3. 40Ar/39Ar ages and paleomagnetism of São Miguel lavas, Azores (Dataset)

   https://doi.org/10.7288/V4/MAGIC/19574  

   Johnson, Catherine L; Wijbrans, Jan R; Constable, Catherine G; Gee, Jeff; Staudigel, Hubert; Tauxe, Lisa; Forjaz, Victor-H; Salgueiro, Mário (June 2022, Magnetics Information Consortium (MagIC))

   Paleomagnetic, rock magnetic, or geomagnetic data found in the MagIC data repository from a paper titled: 40Ar/39Ar ages and paleomagnetism of São Miguel lavas, Azores 

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4. 40Ar/39Ar and K-Ar chronology of Pleistocene glaciations in Patagonia

   Singer, B.S. (January 2004, Geological Society of America bulletin)
5. Rapid preservation of Jehol Biota in Northeast China from high precision 40Ar/39Ar geochronology

   https://doi.org/https:/doi.org/10.1016/j.epsl.2022.117718 0012-821X  

   Youjuan Li, Brian R (July 2022, Earth and planetary science letters)